In the medical field, implantable leads are used with a wide variety of medical devices. For example, implantable leads are used with implantable cardiac pacemakers that provide therapeutic stimulation to the heart by delivering pacing, cardioversion or defibrillation pulses via the leads. Implantable cardiac pacemakers deliver such pulses via electrodes disposed on the leads, e.g., near distal ends of the leads. Implantable medical leads may be configured to allow electrodes to be positioned at desired cardiac locations so that the pacemaker can deliver pulses to the desired locations.
Implantable medical leads are also used with other types of stimulators to provide, as examples, neurostimulation, muscular stimulation, or gastric stimulation to target patient tissue locations via electrodes on the leads and located within or proximate to the target tissue. As one example, implantable medical leads may be positioned proximate to the vagal nerve for delivery of neurostimulation to the vagal nerve. Additionally, implantable medical leads may be used by medical devices for patient sensing and, in some cases, for both sensing and stimulation. For example, electrodes on implantable medical leads may detect electrical signals within a patient, such as an electrocardiogram, in addition to delivering electrical stimulation.
For delivery of cardiac pacing pulses to the left ventricle (LV), an implantable medical lead is typically placed through the coronary sinus and into a coronary vein. However, when located in the coronary sinus or a coronary vein, an LV lead may also be located near the phrenic nerve. Phrenic nerve stimulation is generally undesirable during LV pacing therapy. In some instances, the implantable lead may need to be specifically positioned to avoid phrenic nerve stimulation during LV pacing therapy, which may result in placing the electrodes of the LV lead at a non-optimal site for LV pacing.
In some cases, implantable medical leads with ring electrodes are used as an alternative to cuff electrodes for delivery of neurostimulation to the vagal nerve. However, when located near the vagal nerve, the implantable medical lead may also be located near neck muscles. Stimulation of neck muscles is generally undesirable during therapeutic vagal stimulation.